Processes and products for forming photographic images in color



May 9, 1961 H. G. ROGERS 2,983,606

PROCESSES AND PRODUCTS FOR FORMING PHOTOGRAPHIC IMAGES IN COLOR Filed July 14, 1958 5 Sheets-Sheet 1 x Layer Conlqining Dye Developer I4 I or E|ernen+ I00 Hi Supper? Mat /-Pho+osensl+lve Layer I70 w Prinf Receiving Layer I50 er Elemen+ FIG. 2

Con'l'qiner INVENTOR BYE 1444.014

ATO'RNEYS y 9, 1961 H G. ROGERS 2,983,606

PROCESSES AND PRODUCTS FOR FORMING PHOTOGRAPHIC IMAGES IN COLOR Filed July 14, 1958 3 Sheets-Sheet 2 Blue Sensil'ive a W {Silver Halide Sl'ralum 52 {Yellow Dye Developer S'l'rul'urn 4O FlG. 4

64*Green Sensil'ive Silver Halide Sl'rql'um ZAMGQQI'H'G Dye Developer Sl'rq'l'um 63-Insulo+ing Slrql'um FIG. 5

75-Fil+er S'lralum 74"Red Sensll-ive Silver Halide S'l'rul'um 72 "Cyan Dye Developer S'l'rul'um 50 73-' Insulu+ing Sl'rql'um FIG. 6

loo 50 W l F l5 FlG. 7

lNVENTOR M y/6 M WWW BY M May 9, 196] EE 2,983,606

H. G. RO PROCESSES AND PRODUCTS FOR FORMING PHOTOGRAPHIC IMAGES IN COLOR Filed July 14, 1958 3 Sheets-Sheet 3 '50 Support Image- Receiving Layer :3: -Photosensitive Layer IE ll Spreading Sheet FlG. 8

Image- Receiving Layer Rupturable Container Holding Processing Composition Blue-Sensitive Emulsion Layer Containing Yellow Dye Developer 5 Spacer Layer 8O Green-Sensitive Emulsion 62 Layer Containing Magenta Dye Developer Spacer Layer Red-Sensitive Emulsion Layer Containing Cyan Dye Developer Support NVENTOR. M

BY 531M -24 AT RNEYS United States Patent PROCESSES AND PRODUCTS FOR FORMING PHOTOGRAPHIC IMAGES IN COLOR Howard G. Rogers, Weston, Mass, assignor to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware Filed July 14, 1958, Ser. No. 748,421

45 Claims. (Cl. 96-29) This invention relates to the art of photography and, more particularly, to processes for the formation of dye images.

Objects of the invention are to provide novel processes for forming monochromatic as well as multicolor pictures by transfer and reversal practices wherein a single reagent is utilized for the formation of a negative image as well as a positive image of said negative and wherein the quantity of reagent which is available for positive image formation is controlled as a function of the development of the silver halide latent image, said development providing, as an oxidation product of said reagent, a substance which is substantially immobile in a photosensitive element while depositing the unreacted reagent on a print-receiving material to dye the same and provide said positive image. This procedure overcomes certain practical and theoretical limitations in prior transfer processes by making it possible to utilize a single reagent for the formation of each color instead of the use of several reagents, by avoiding the synthesis of each color component during processing and the attendant disadvantages of such synthesis, and by unexpectedly offering a wider selection of both dye and developer types for composite reagents of this nature.

Other objects of the invention are to provide processes of the character described wherein a dye image is formed, by transfer, using a reagent which is a dye possessing a developing function and which, when oxidized, provides a reaction product of lower solubility in a processing liquid than the unreacted reagent; to provide processes wherein such a dye-providing reagent, namely a dye developer, is utilized in a predetermined quantity; to provide such processes wherein a dye developer is employed which possesses a tanning action upon the carrier material for silver halide and wherein said dye developer is utilized in excess of the quantity thereof needed for the development of a fully exposed unit portion of photosensitive silver halide, and its ability to tan or harden gelatin or other carrier material for silver halide is employed in the control of the transfer of the unreacted reagent; to provide processes wherein the dye developer is utilized not only to control its own transfer but in addition to control the transfer of another colorant or dye; and to provide processes wherein the sequence of operations necessary to form a positive print of a latent negative image is initiated by permeating a photosensitive element containing latent image with a liquid processing composition which is a solvent for dye developers in unreacted condition.

Further objects of the invention reside in the provision of processes of the character described for the formation of dye images of dyes which are of subtractive 2,983,606 Patented May 9, 1961 colors, and especially processes for the formation of monochromatic dye images, black dye images and multicolor images; and in the provision of processes wherein latent image records present in a photosensitive element which has been exposed to an object and. which are individually representative of a predetermined color component of said object are processed with individual dye developers to provide, in a print-receiving element and for each latent image record in said photosensitive ele-.

ment, a dye image which is of a predetermined color and which is a reverse image of said latent image record.

A further object is to provide processes utilizing dye developers to provide monochrome, black and multicolor transfer images, wherein dye developers are utilized in combination with a silver halide developing agent which is not a dye.

A further object is to provide processes, as mentioned above, whereinat least a portion of the dye developer immobilized, as a function of development, is immobilized by reaction with an oxidation product of said silver halide developing agent which is not a dye, said oxidation product being formed by development of exposed silver halide.

Additional objects are to provide products useful in performing the above mentioned processes.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

Figure 1 is a diagrammatic side elevation of one embodiment of a film unit especially suited for the formation of monochromatic or black and white images;

Fig. 2 is a diagrammatic elevation of another embodiment of filirl unit similar to that of Fig. l;

i Fig. 3 is a diagrammatic perspective view of a preferred embodiment of a negative photosensitive element provided with a plurality of sets of selectively sensitive silver halide elemental portions and useful in carrying out multicolor image formation by transfer processing;

Figs. 4, 5 and 6 are broken-away elevations of a photosensitive element similar" to that of Fig. 3 in which the selectively sensitive elemental portions thereof are each provided bya composite type of layer comprising two or more strata;

Fig. 7 is a schematic side elevation of a photographic film unit which employs a photosensitive element similar to that of Fig. 1 in association with a print-receiving element and a rupturable container holding a liquid process- In general, the photographic processes and products disclosed herein are concerned with the treatment of a latent negative image in a photosensitive silver halide layer whereby to provide a dye positive image in or on a print-receiving element comprising an image-receiving layer.

United States Patents Nos. 2,559,643 and 2,661,293 disclose processes of the character just, noted and wherein a liquid processing composition is permeated into a silver halide layer of a photosensitive element, and a pair of reagents, soluble in the liquid and reactable with one another in the presence of an oxidizing agent to provide a dye, are utilized in solution in the liquid composition to develop latent image in the silver halide and form therein silver and dye images as well as an imagewise distribution of unreacted portions of said two reagents which at least in part are transferred by imbibition to a print-receiving element holdable in superposed relation to the photosensitive element and are there reacted in the presence of an oxidizing agent to provide a dye image which is a reverse image of said latent image. The print-receiving element and the photosensitive element are separated from their superposed relation at some stage of processing after the unreacted portions of the two reagents have been transferred to the printreceiving element. One of the reagents disclosed in these just-mentioned patents is a conventional secondary silver halide color developer, for example p-phenylenediamine or derivatives thereof, while the second reagent is a conventional coupler, for example a phenol, naphthol, pyrazolone or acetanilide type of coupler.

Other and related disclosures for the formation of dye images by transfer processing which utilize a secondary silver halide color developer and a conventional coupler are set forth in United States Patent No. 2,647,049, as well as in application Serial No. 94,647, filed May 21, 1949, by Edwin H. Land (now Patent No. 2,698,798, issued January 4, 1955), application Serial No. 176,961, filed August 1, 1950, by Edwin H. Land (now abandoned and replaced by application Serial No. 448,441, filed August 9, 1954, now US. Patent No. 2,968,554, issued January 17, 1961), and in my application Serial No.

358,011, filed May 28, 1953 (now abandoned and replaced by application Serial No. 577,711, filed April 12, 1956).

In addition, my application Serial No. 358,012, filed May 28, 1953 (now Patent No. 2,774,668, issued December 18, 1956) and my copending application Serial No. 613,691, filed October 3, 1956, which is a continuationin-part of said application Serial No. 358,012, disclose procedures for providing a dye image by transfer which also utilizes two reagents capable of being reacted with each other. However, in my said applications, while one of the reganets is a secondary color developer for silver halide, I have disclosed as the second reagent a complete dye, as distinguished from a coupled, which is soluble in alkaline solution and which is reactable with the oxidation product of the developer.

The procedures heretofore discussed for forming a dye image by transfer on a print-receiving element involve two reactions in the photosensitive element employed. The developer must react with the latent'silver halide in the photosensitive element and its reaction product must then react with a conventional coupler or a complete dye. Thus, in the previously-mentioned practices, two reactions are required to control the transfer of dye or dye-forming components from the photosensitive element to the print-receiving element. In generat, in the case wherein a conventional coupler and an unoxidized silver halide color developer'are transferred to the printreceiving element, these two reactions are repeated by effecting the oxidation of the transferred developer.

The present invention is concerned with improvements in procedures utilized in the aforementioned patents and applications for the formation of dye images and espe- .4 cially for the formation of dye images by one-step photographic transfer processes. Accordingly, the invention will be described in connection with such transfer processes and products useful for carrying out the same.

The improvements herein are effected by the employment of developers which are dyes themselves and by the utilization of the unreacted portions of such a developer to provide a dye image on the print-receiving element. Developers of this nature may be called dye developers. By a dye developer, I mean a developer which is characterized by being a dye itself and which possesses a silver halide developing function.

Important features and advantages of the processes described herein reside in the use of a single reagent for the development of silver in a photosensitivelayer and for the formation of a dye image in a print-receiving element. In a preferred embodiment, the single reagent is utilized for carrying out of a single reaction within the photosensitive element which, by its development of silver, controls the transfer of dye to the print-receiving element. As a variant, the invention contemplates the utilization of this reagent, namely, the dye developer, in conjunction with a second reagent, namely, another colorant, to the end of controlling the transfer of the second reagent which may be of a character that is reactable or unreactable with the oxidation product of the first reagent.

Other advantages and features reside in the use of developers which are not only colored themselves but are capable of carrying out a tanning or hardening action upon gelatin or other carrier material for silver halide during the course of development of a latent image in a silver halide emulsion. The tanning or hardening action of the dye developer permits the developer to be incorporated in vthe photosensitive element in a quantity per unit portion of photosensitive silver halide which is in excess of-that quantity needed to completely develop each said unit portion if completely exposed. The excess dye developer available for transfer to the printreceiving element from unit portions of the photosensitive element which have not been exposed or have been less than completely exposed provides means for increasing the contrast and density of the positive image provided on the print-receiving element.

Still other advantages and features reside in processes for forming dye images by transfer without oxidation of the transferred developer, thus avoiding an oxidizing reaction in the print-receiving element or the employment therein of an oxidizing agent.

In a general sense, the art is aware of the existence of dye developers. For example, reference is made to 4-phenyl-azo-1,2-dihydroxynaphthalene reported in History of Color Photography by Joseph S. Friedman (1944 Edition, American Publishing Company, Boston, Massachusetts) on page 400. Additionally, dye developers form the subject matter of US. Patent No. 2,543,691, issued to Joseph S. Friedman on February 27, 1951, for Azo Dyes as Silver Halide Photographic Developing Agents. However, in all instances disclosed by theprior art, dye developers have been used solely for the purpose of developing latent image in a photosensitive silver halide layer to silver and for forming a dye image in situ with the developed silver image and have been utilized in processes wherein the silver is removed from the photosensitive layer to leave the dye image or the oxidation product of the silver halide development. In other instances, dyes which are, in fact, dye developers, have been described but the art has not utilized them to form dye images or as photographic developing agents.

Dyes of substantially all clases, with certain exceptions, are available for use in carrying out the invention. In general, most dyes lackthe ability to develop latent image present in silver halide so that it becomes necessary to add or to attach to the dye molecule a developing function. Practices for adding a developing function to a dye are hereinafter set forth. Dyes employed in carrying out the invention should not, as for example sulfide dyes, possess constituents which are harmful to photographic materials such as silver halide. In the event the dye molecule of the dye developer is of a nature which tends to desensitize silver halide, suitable precautions, such as those mentioned in my previously-mentioned application Serial No. 358,011 (now abandoned and replaced by application Serial No. 577,711, filed April 12, 1956),'should be utilized for controlling this undesirable condition. Subject to these qualifications, any dye may be employed, which is soluble in solutions of photographic reagents, such as alkaline solutions, which possesses a developing function and which provides, as an oxidation product, a substance having a lower mobility than theunoxidized dye developer in solutions of photographic reagents.

While usually the color characteristics of the oxidation product of the dye developer will be similar to the color characteristics of the unoxidized dye developer, color differences between these substances are immaterial when carryingout a one-step transfer process since the transferred dye developer will be employed for image formation in a substantially unoxidized state. Thus, a wider field for the selection of dyes available for photographic processing is presented. In someinstances, however, a color change on oxidation may be useful in obtaining images of desired characteristics. The important feature is that the dye developers are capable of providing an image withoutoxidation after transfer.

As particular examples of dyes which are utilizable in carrying out my practices, I mention azo dyes and anthraquinone dyes to which one or more hydroquinone groups have been attached. In this instance, the hydroquinone groups provide the developing function of the dye. Other suitable dyes include azo dyes to which, as a developing function, an amino naphthol or a p-methylaminophenol has been attached.

In general, dye developers are easily synthesized. For example, the methods of attachment of hydroquinone to a dye molecule may be through amino, sulfonyl or carboxyl groups. More specifically, dyes having a free amino group may have one or more hydroquinone de veloping functions attached to the dye molecule by reacting an amino hydroquinone, the dye and cyanuric chloride. Also, a dye developer of the hydroquinone type may be formed by condensation reaction wherein the hydroquinone and the dye are condensed through a sulfonyl or carbonyl group. The developing function can be a part of the dye itself, as for example the amino naphthol group in the dye developer, 1-amino-2-naphthol- 4-azobenzene. When the developing function is a part of the dye, it will affect the color thereof. Also, the developing function can be insulated from the dye molecule in such a way that it adds little if any color of its own, as disclosed and claimed in the copending U.S. application of myself and Elkan R. Blout, Serial No. 485,840, filed February 3, 1955. An example of this latter practice occurs when hydroquinone is attached through a sulfonyl group to the dye molecule. These and other dye developers will be referred to in more detail hereinafter. w

In the practice of the invention, the dye developers are selected for their ability to provide colors useful in carrying out subtractive color photography. In this regard, dye developers possessing an appropriate yellow color are Z-naphthylazohydroquinone and phenylazohydroquinone. Examples of suitable magenta colored dye developers are 2-hydroxynaphthylazohydroquinone and 1-amino-2-naphthol-4azobenzene. An example of a suitable cyan colored dye developer is 1,4-bis-(2',5'-dihydroxyanilino) anthraquinone. Other suitable dye developers will be mentioned later.

Dye developers of the various subtractive colors are utilizable individually to provide individual cyan, yellow and magenta images, as well as black dye images. Appropriate dye positive images of the three subtractive colors may be formed, in a manner similar to that disclosed in Patent No. 2,647,049, by appropriate dye developers on individual print-receiving elements which, after image formation therein, are mounted in superposed and registered relation to provide 'a multicolor picture, or the individual transfer images may be successively formed in registered relation 'on a single print-receiving element. The present invention also includes the use of dye developers of the three subtractive colors in an appropriate mixture in which the quantities of the developers are proportioned so that the colors of the dye developers add up to black whereby to obtain a black-and-white transfer image.

Furthermore, dye developers of the nature with which this invention is concerned are useful in light-sensitive elemental portions of minute size which are mounted upon a suitable support in a color screen pattern and which are individually exposable wherebyto permit the formation of a multicolored image on a print-receiving element. Suitable film structures for carrying out this embodiment of the invention are disclosed in the previously-mentioned applications Serial Nos. 176,961 (now abandoned and replaced by application Serial No. 448,441, filed August 9, 1954, now U.S. Patent No. 2,968,554) and Serial No. 358,011 (now abandoned and replaced by application Serial No. 577,711, filed April 1 2, 1956).

A preferred embodiment of a photographic film assembly useful in carrying out a one-step photographic process for the formation of a dye image of an individual color or of a black-and-white image is illustrated in Fig. 1 as comprising a photosensitive element 10 superposed on a print-receiving element 15 with a rupturable container 17 for a liquid processing composition mounted therebetween.

The photosensitive element 10 comprises a conventional paper or plastic film base 11, a layer 12 containing a dye developer and a photosensitive layer 14 comprising a suitable silver halide emulsion. Also, silver halide emulsions of suitable nature are disclosed in previously-mentioned patents and applications. Preferably, silver halide emulsions are employed wherein gelatin is the carrier for the silver halide. However, the invention may be practiced with any of the many other and wellknown carriers for silver halide.

The container 17 may be formed of a composite sheet material comprising an inner layer which is substantially chemically inert to the liquid composition used for processing the film unit, an intermediate layer which is substantially impervious to vapor and an outer or backing layer which can be readily adhered to one layer of the film assembly, such for example as the print-receiving element 15. Suitable containers for this purpose are disclosed in U.S. Patent No. 2,500,420, as well as in the previously-mentioned Patent No. 2,559,643.

The print-receiving element 15 comprises a dyeable material and may, as shown, comprise a single print-re ceiving layer or a print-receiving layer may be secured to a support. Nylon is a preferred material for the print-receiving layer, preferably a nylon such as N-methoxymethyl polyhexamethyl adipamide and which is available under the name of Nylon Type 8 from E. I. du Pont de Nemours & Company. Other materials suitable for print-receiving layers comprise a partially hydrolyzed polyvinyl acetate such as that commercially available under the name of Vinylite MA-28-18 from Bakelite Division, Car-bide & Carbon Chemicals Co.; polyvinyl alcohol with or without plasticizers; baryta paper, i.e., a support having a baryta coating thereon; cellulose acetate with filler, as for example one half cellulose acetate and one half oleic acid; gelatin; and others of similar nature.

In the formation of the photosensitive element 10, the dye developer, aspointed out, is distributed within a.

layer 12. A composition for forming the layer 12 comprises cellulose acetate hydrogen phthalate in which the dye developer is included. This composition is coated or' otherwise applied onto the support 11 to provide the dye developer layer or stratum 12. Other materials in which the dye developer may be incorporated for application or mounting upon a support include shellac and gelatin,as well as polymers of various types.

After the dye developer has thoroughly dried, the emulsion 14 is coated or otherwise applied thereon.

In the formation of the layer 14, the composition comprising the dye developer is easily applied by tray coating practices wherein one surface of the support is brought into contact with composition which is carried in a tray or other container. Roll coating procedures and doctoring techniques are available for the application of suificiently viscous compositions onto a support.

A composition which contains dye developer and which is suitable for application by tray coating practices comprises:

1 g. dye developer .4 g. cellulose acetate hydrogen phthalate 80 cc. acetone 20 cc. methanol cc. ethyl Cellosolve (ethylene glycol monoethyl ether) 5 g. dye developer 25 g. cellulose acetate hydrogen phthalate 100 cc. acetone A typical formulation for the liquid processing composition in container 17 for use with the film assembly of Fig. 1 comprises:

5 g. sodium carboxymethyl cellulose 1 /2 g. sodium'hydroxide 100 cc. water The liquid processing composition contains a solvent for the dye developer and generally is of a viscous nature, as is the case of the composition in the just-noted formulation. However, it is not an essential of the invention to employ a viscous liquid. Thus, the viscosity-imparting agent, namely the film-forming material, such as the sodium carboxymethyl cellulose, may be omitted therefrom. The processing composition may be applied in any desired manner, e.g., by spreading, dipping, spraying, immersing, etc. Other formulations of processing compositions adaptable for use in the present invention are disclosed in the herein mentioned patents and applications. In further regard to the liquid processing composition,

it is at times desirable, depending upon the particular photographic emulsion and/or dye developer which is employed, to add sodium bromide to the formulations given above. This may be done to the extent of 0.05 g. per 100 g. of viscous reagent and is for the purpose of preventing the fogging of the photosensitive emulsion. Likewise, in certain instances, it may be desirable to substitute a volatile alkali such as diethylamine for the hydroxide of the liquid processing composition to control 'the pH of thefenvironment of the transferred dye developer. Furthermore, with certain dye developers such as phenylazohydroquinone, the volatile alkali is effective to speed up developing rate and to increase the quantity of dye developer transferable for positive image formation in the print-receiving element and thus produces transfer images of high density and contrast.

It should also be noted that certain dye developers, e.g., dye developers in which the hydroquinone group becomes a part of the conjugated system, are subjectto color change in accordance with the pH of the'environment in which they are contained or located. As examples of such developers, mention-may be made of phenylazohydroquinone which is dark blue in strongly alkaline solutions and yellow in neutral or acid solutions.

Where dye developers of this character are employed, it is necessary to assure that the pH value of the environment in which the transferred and unreacted dye developer is deposited is of a nature suited to impart the desired color to the transferred dye developer or is capable of attaining a desired pH value since the dye developer is rendered effective to carry out its developing and imageforming functions by solution in an alkaline liquid processing composition. In instances where the alkali of the processing liquid is a hydroxide, the fact that the hydroxide becomes carbonated after processing and by contact with the air will be eifectiveto provide the desired reduction in pH; Attainment of the desired pH value for the environment of the transferred dye developer may be more'quickly achieved by'the use of a volatile alkali such as diethylamine in the processing liquid. Further control of this nature resides in the utilization of a material for the print-receiving layer which is diflicultly penetrable by alkali, for example, an appropriate nylion such as Nmethoxymethyl polyhexamethylene adiparnide or by the employment of a print-receiving layer in which an acid or an acid-forming compound, for example oleic acid, has

'been incorporated.

While dye developers which include a developing function as part of their conjugated system are particularly sensitive to changes in the pH of their environment, it is pointed out that insulation of the developing function, such as hydroquinone, from the conjugated system pro vides dye developers of reduced pH sensitivity.

In all products employed in the practice of the invention, it is preferable to expose the negative material or photosensitive element 10 from the emulsion side. It is therefore desirable to hold the photosensitive element 10 and positive sheet material 15 together at one end thereof by fastening means, not shown, but comprising hinges, staples, or the like, in such manner that the photosensitive element 10 and the positive element 15 may be spread apart from their positions illustrated in Fig. 1. When the film unit is of the roll film type, the photosensitive element 10 and the positive sheet 15 are wound into separate rolls and the free ends of said rolls are connected together in the manner described. In addition to film units of the roll film type, it is also contemplated to use film units of the film pack and sheet film types.

A camera apparatus suitable for processing roll film of the type just mentioned is provided by the Polaroid Land Camera Model 95, sold by the Polaroid Corporation, Cambridge, Massachusetts, or similar camera structure, such for example as the camera forming the subject matter of Patent No. 2,435,717. Camera apparatus of this character permits successive exposure of individual frames of the photosensitive element 10 from the emulsion side thereof, as well as individual processing of an exposed frame, by bringing the exposed portion of the photo sensitive element 10 in superposed relation with a portion of the print-receiving element 15 while drawing these portions of the film assembly between a pair of pressure rolls which rupture the container associated therewith and spread processing liquid between and in contact with the photosensitive element and the corresponding registered area of the print-receiving element.

By way of explaining the formation of a dye image by by imbibition to the print-receiving element 15.

transfer, consider the film unit of Fig. 1 as having been exposed to provide a negative latent image and as having la=dye developer of a desired color, for-example magenta,

distributed in the layer 12 thereof. Processing of the film assembly of Fig. 1 proceeds by permeating the photosensitive element with processing liquid applied in contact with the photosensitive element upon drawing are stripped apart following the deposit on the printreceiving element of the dye image-forming components which provide the transfer image. It is to be noted that it is within this lamination that the single reagent for providing the dye image, i.e., the dye developer, on the print-receiving element is located.

The spread processing liquid permeates ormigrates into the photosensitive layer .14 and the dye developer layer 12. During the permeation into the layer 12, unreacted dye developer contained in this layer is dissolved in the processing liquid and is transported, in solution, into the photosensitive layer 14 to distribute unreacted dye de veloper in the photosensitive layer.

Where 'thedye developer, transported to the photosensitive layer 14, reacts with the exposed silver halide, it is oxidized as a function of the amount of silver halide reduced to silver while the oxidation product of the developer forms an image that is substantially coextensive with the developed silver. Preferably, the dye developer utilized is selected for its property of having an oxidation product as a result of silver development which is of considerably lower solubility in the liquid processing composition than the unreacted dye developer itself. Under these conditions, the oxidation product is substantially immobilized or retained in the photosensitive layer 14. In the event that the oxidation product lacks the desired low solubility, procedures, which will be hereinafter explained, are utilized for retaining the oxidation product in the photosensitive element.

It is this means, namely the formation of an insoluble oxidation product, i.e., an oxidation product which is at least sufficiently less soluble so that it will not difiuse to the image-receiving layer during imbibition, that provides the principal mechanism for controlling the transfer of dye image-forming components to the print-receiving element. Thus, portions of the dye developer which have become oxidized are exhausted or made unavailable for dye image formation on the positive or printreceiving element. As heretofore noted, the tanning ability of a dye developer may be utilized as a further or secondary control mechanism for the transfer of dye. A stillfurthe! control mechanism is believed to be the decrease in the solvent power of the processing solution in exposed areas due to localized exhaustion of alkali in such areas as a result of the development.

At the time that the dye developer is developing silver and providing an insoluble oxidation product, an image- Wise distribution of unoxidized and unreacted dye developer is formed in the negative material in places where unexposed silver halide grains are present or in places where exposure and subsequent development is less than complete. Dye developer present in solution in this imagewise distribution is transportable, at least in part, The print-receiving element is dyed or otherwise colored by the transported and unreacted dye developer where the dye developer is deposited to provide the desired reverse 10 image in color of the latent image. In the assumed instance, the transfer or positive image is magenta. After formation of the positive image, the print-receiving element and photosensitive element are separated.

From the foregoing, it will be apparent that the color of the oxidation product of the dye developer is immaterial since the positive image is formed of the unoxidized and unreacted dye developer. This is advantageous since it avoids the use of an oxidizing agent in the printreceiving element. Likelihood of the transferred dye developer becoming oxidized from contact with the atmosphere is negligible since these materials are oxidizable substantially only by a strong oxidizing agent and at a relatively high pH, as for example by exposed silver halide in the presence of sodium hydroxide. At a lower pH, particularly at a neutral or an acid pH, the dye developers employed herein are quite stable to oxidation by air. This has been demonstrated in actual use of dye developers which have a different color oxidation product. It should also be noted that in most cases so long as the dye developer is in an acid or neutral environment, both its oxidized and unoxidized forms will be of the same color.

The print-receiving element, when stripped from the photosensitive element, will contain substantially only dye developer which provides the desired color positive image. In this regard, the print-receiving element, during the processing thereof, is maintained free of appreciable amounts of material which, during the processing of the film unit or which in the presence of light and air, will impart to the print-receiving element a color that will adversely affect the visibility of the image of dye developer formed therein.

By employing a dye developer having a developing function, such as a hydroquinone or catechol developing function, which is able to tan the gelatin of a photosensitive silver halide emulsion, it becomes possible to use dye in excess of that controllable by the development of latent silver halide and is of assistance in providing positive prints of high density and contrast by permitting a build-up of the shadows of the positive print Without coloring the highlights thereof. In general, dye developers having a dihydroxy benzene developing function or a trihydroxy benzene developing function provide the most efficient tanning action. For utilizing the tanning action of the developer as a dye transfer control mechanism, the dye developer should be preferably located in a layer between the photosensitive layer and the support, as shown in the photosensitive element 10, although the layer 14 may be dispensed with and the dye developer incorporated in the photosensitive layer 12.

The use of a dye having a developing function for the formation of an image in one step by transfer on a print-receiving element is distinguishable from practice which dissolves a dye having no developing function in a tanning developer and permeates a silver halide element having a negative latent image with the developer and dye solution to develop silver and restrain or immobilize dye in the regions of the silver developed by the tanning action of the developer While transferring unreacted developeran'd dye in solution to form a positive dye image on a print-receiving element located in superposed relation to the negative. It is extremely diliicult to utilize the hardening action of a separate tanning developer to control the transfer from a photosenstive element of a dye which contains no developing function and which is sufficiently soluble in the developer to build up high densities 011 a print-receiving element. When a separate tanning developer and a dye dissolved therein are used in the manner described so that development of silver and transfer of dye occur simultaneously and in one step, very little tanning action has taken place in fully exposed regions of the photosensitive element by the time that the dye has started to transfer. Contrary to this, a dye developer will, as a result of silver de 'velopment, be precipitated in the photosenstive element in a form such that it will not transfer and by the time the dye in excess of that controllable by the development of a fully exposed portion is ready to transfer, the completely exposed portion has been fully tanned to provide likely to stain the highlights of the positive image as well as to degrade the color or dye thereof, whereas with a dye developer not only are the oxidation products immobilized in the negative to avoid highlight stain but also the developer which has transferred is the desired color.

From the foregoing, it will be appreciated that the utilization of the ability of a dye developer molecule to tan or harden the carrier material for the silver halide, as well as to provide a dye image by transfer, is completely different from the use of a solution of a dye and a separate tanning developer in carrying out a one-step transfer process. Certain of the dye developers herein set forth possess an ability to tan gelatin, the usual carrier material for silver halide.

In addition, a dye developer which possesses a free amino group as part of its developing function may be utilized to harden a carrier material for silver halide such, for example, as a polymer which is normally permeable to alkaline solutions but which can be made less permeable by a coupling reaction with oxidized dye developer. One specific example of a polymer of this nature is a modified polyvinyl alcohol wherein positions on its chain have been substituted with phenol or naphthol and wherein the substituted phenols or naphthols have open positions for coupling which are para to hydroxyl groups. Another example occurs where the polyvinyl alcohol has been substituted with a compound containin a reactive methylene group which is available for coupling. The incorporation of light-sensitive silver halide in polymers of the character mentioned is understood by the art, an example thereof being disclosed in US. Patent No. 2,397,864.

If the coupling group forms the only substitution of the polymer, its permeability to alkaline solutions is radically lowered upon coupling with the oxidation product of a developer having a free amino group which is part of its developing function and which is available for coupling.

The tanning or hardening of the carrier material for silver halide as a result of development provides a control mechanism which is particularly useful in the formation of multicolor positive prints using color screen type elements. For example, in a photosensitive color screen element for use in forming a three-color transfer print, dye developer and silver halide which are available for the provision on a print-receiving element of each individual color image component of a three-color image may be restricted to one-third of that available in an equivalent photosensitive element which is used for forming a monochromatic image by transfer. Theoretically, to compensate for such a reduction in the dye developer and silver halide available for multicolor image formation, it is desirable to obtain three times the dye density and contrast from the dye developer and silver halide usable for the formation of each component image on the printreceiving element. The use of this tanning mechanism provides means for obtaining high density and contrast in the finished multicolor print.

' When no mechanisms to control the transfer of excess dye developer are employed or where the dye developer is not incorporated in the photosensitive element, it is preferably used in a quantity per unit portion of the emulsion suflicient to effect the complete development of said unit portion if the unit portion is fully exposed.

When mechanisms for controlling the transfer of excess dye developer, such for example as those mentioned hereinbefore, are employed, the dye developers may be used in excess of the quantity indicated above.

The reagent or dye developer is intended to be so distributed within the lamination provided by superposing the photosensitive and print-receiving elements as to have a substantially uniform concentration per unit surface area of this lamination. In this regard, the reagent may also be said to be present per each unit area in at least such quantity as to cause the reagent to be substantially completely reacted in the photosensitive element in the event of the full development of the silver halide of a unit surface area or it may be in excess of this quantity.

While all processing has heretofore been described in connection with the use of a single reagent which develops the negative and dyes the positive material to provide a dye image, useful variations of the invention employ an additional reagent or colorant in the photo sensitive element and utilize the dye developer to control the transfer of the second reagent as well as itself.

As one example of practice which employs a dye developer and another colorant, and which is particularly useful for increasing the density and contrast of the positive print, the invention intends to use in the photosensitive element a dye developer having a free amino group as a part of its developing function together with a colored component such as a dye of the character disclosed in my previously-mentioned copending applications and comprising a dye which is capable of coupling with the oxidized dye developer and providing a reaction product which is substantially immobile or may be immobilized in the photosensitive element. Where such reactants are employed, the dye developer will develop the exposed silver halide in the photosensitive element and couple with the unreacted dye present in the photosensitive element, while in portions of the photosensitive element where no exposure has occurred, or which are less than completely exposed, both the dye developer and the unreacted dye will be transferred to a printreceiving element to provide a reverse image in color thereon.

Dyes which are particularly suited for reaction with an oxidation product of a developer are found in those dyes having an open position on a ring, which position is para to a hydroxyl or an amino group, or those dyes having a reactive methylene group. Many suitable dyes coming within this classification are found among the azo, pyrazolone and triphenyl methane dyes.

The employment of a coupling dye in conjunction with a dye developer makes it possible to substantially double the density of the dye image formed by transfer for the same quantity of exposed silver halide in the photosensitive element. At the same time the use of a colorant, in addition to the dye developer, makes it possible to form a mixture of dyes on the positive element which would possess light-transmitting and absorption characteristics of a nature improved over that of either the coupling dye or the dye developer.

The procedure just described wherein a dye and a dye developer are employed together is not limited to socalled coupling dyes but may be extended to dyes which lack a coupling function, provided they have a relatively slow transfer rate and are employed with a gelatin tanning type of dye developer and especially a developer of this nature which possesses a fast developing rate.

As heretofore indicated, the oxidation product of a dye developer is of lower solubility in the liquid. processing composition than the unoxidized and unreacted developer. In instances Where the solubility of the oxidation product of a dye developer is not sufficiently low to prevent its transfer to a print-receiving element, it is possible vto carry out the invention with the use of'a dye 1 liquid processing reagent. viscous processing composition is particularly applicable and may be applied to the negative material by imbibition phenol or diamino benzene which, on oxidation, is able to react with a conventional coupler orother material incorporated in thepho'tosensitive element. For example, a dye developer lacking the desired low solubility for its oxidation product would be incorporated in the layer 12 of the photosensitive element 110, while a coupler would be incorporated in the silver halide layer 14. The coupler in thelayer 14 may be of the immobile or substantially nondiffusing type or it may be immobilized in the photosensitive layer by appropriate practices such as through the use of high-boiling-point solvents. In processing, the oxidized developer couples with a coupler which is immobile in the photosensitive element and thus becomes immobilized. This just-mentioned procedure is advantageous from the standpoint of increasing the availability of dyes of appropriate color.

Several features are common to practices heretofore set forth whether a dye developer is employed by itself or in conjunction with a colorant or a reagent such as an immobile coupler. In all instances, the silver halide developing function is apart of a dye molecule. All procedures possess a common control mechanism for the transfer of dye developer by providing, as a result of its oxidation by silver development, a reaction product which is either inherently possessed of the desired low solubility or which is in a form potentially convertible to a substantially insoluble compound upon further reaction.

Furthermore, by all procedures of the invention, any dye transferred to the receiving sheet is utilized without the need of reacting the transferred dye. In this regard and in the case of a dye developer employed in conjunction with the coupling dye, it will be noted that not only does the dye developer control the quantity of itself which is transferred but that the reaction of its oxidation product with the coupling dye also controls the quantity of the coupling dye which is transferred. Similarly, the dye developer not only controls its own quantity available for transfer but controls the transfer of a dye which lacks invention may be otherwise effected. For example, a

photosensitive layer, after exposure, maybe permeated with the liquid processing composition as by coating, or flowing or spraying the composition onto the photosensintive layer or by bathing the layer in the composition or by otherwise wetting the layer with the composition, following which the permeated layer is brought into contact with the print-receiving element for image formation in the manner heretofore described. It is also withinthe scope of the invention to simultaneously wet the photosensitive element and the print-receiving element with the liquid composition for carrying out the foregoing procedures. Furthermore, the processing composition ,may be applied prior to exposure, in accordance with the procedures disclosed in the copending application of Edwin H. Land, Serial No. 498,672, filed April 1, 1955.

Furthermore, the invention may be successfully practiced without the use of a film-forming material in the As an illustration, a nonor coating practices or by bathing the negative in the composition, and may be similarly applied to the printreceiving element before the latter and the negative material are brought into superposed relation or contact for carrying out the transfer of positive image-forming components.

Fig. 2 illustrates an embodiment of film assembly which permits the dye developer to be located in a variety of lo- "I4 cations and is not dependent upon the incorporation of the dye developer in a layer such as the "layer 12 located between the support 11 and the photosensitive layer 14 as in Fig. l. The film assembly of Fig. 2 employs a photosensitive element 10a and a print-receiving element 15a. The photosensitive element 10a of Fig. 2 comprises a support 11 similar to the support of Fig. land which has coated directly thereon a photosensitive layer .1421.

In the film assembly of Fig. 2, the dye developer may be included in the liquid processingcomposition of the rupturable container 17a, in which event the photosensitive layer 14a will comprise only a silver halide emulsion. Alternately, the dye developer may be incorporated in the photosensitive layer 14a, in which event container 17a will hold only the liquid processing composition, as for example that of the previously given typical formulation.

The practice of dissolving the dye developer in the liquid composition prior to permeation of the liquid into the photosensitive element is usually restricted to the formation of monochromatic or blackand-white prints in individual layers whereas the practice by which the dye developer is included in the photosensitive layer 14a or anywhere within the photosensitive element itself may additionally be employed for the formation of three-color prints in one step. t

In lieu of having the photosensitive layer and the image-receiving layer located in 'two separate elements, it is also within the scope of this invention to coat the photosensitive layer over the image-receiving layer, so that both layers are contained in the same element. An example of such a structure is shown in Fig. 8, wherein an image-receiving layer 15a is coated on a support 11, and the photosensitive layer 14a is coated over the imagereceiving layer 15a. Processing is effected by rupture .of a container 17a and spreading. its contents between the photosensitive layer 14a of the combined negativepositive element and a spreading sheet 11 which facilitates spreading. The dye developer may be located in the rupturable container 17a or in the photosensitive layer 14a. It will be apparent that the processing composition must permeate through the photosensitive layer 14abefore reaching the image-receiving layer 15a. After transfer has been effected, the image transferred to the imagereceiving layer 15a may be viewed by stripping away the spreading sheet 11. The layer of processing composition and the photosensitive layer 14a adhere more strongly to the spreading sheet 11 than to the image-receiving layer 15a, and are removed with the spreading sheet .11. If desired, a suitable stripping layer may be applied between the image-receiving layer 15a and the photosensitive layer 14a to facilitate this stripping. Structures of this type are described in US. Patent No. 2,661,293, issued to Edwin H. Land on December 1, 1953, and particularly with respect to Fig. 7 of said patent. i

It is desirable that the dye developer, when utilized in photosensitive layer, be employed so that it has low covering power whereby it will exert negligible absorption upon light which is used to expose the photosensitive element. For this reason, the dye developer, when incorporated in the photosensitive layer, is utilized in relatively large particle sizes.

Procedures for incorporating a developer or a dye 'in a silver halide emulsion are well known to the art and need no detailed discussion. However, it may be pointed out that many practices employable for incorporating a dye developer in a silver halide emulsion. are disclosed in previously-noted applications and in certain of the patents heretofore mentioned.

As a still further practice, a dye developer may be coated upon the surface of the image-receiving layer 15a which is contacted by the processing liquid. In this instance, the dye developer should be heldsufficiently loosely so that at fully exposed portions of the negative, the transfer of the dye developer to the photosensitive of the materials which assist in image formation. embodiment, the light-sensitive emulsions are present in 1y onto that elemental portion. from the standpoint of the association of filter media with 15 element will be substantially complete whereby to assure clear highlights for the. positive print. This practice is available for use in the formation of monochromatic and black-and-white images.

The principles heretofore enunciated are available for multicolor image formation by a one-step process on a print-receiving element used in conjunction with negative material embodying a photosensitive element comprising a support having mounted thereon a plurality of lightsensitive emulsions each comprising silver halide, and all In one the form of a multiplicity of light-sensitive elemental portions. The elemental portions are made up of at least two sets of elemental portions which are selectively sensitive whereby the elemental portions of each set are exposable by light of a predetermined wavelength. Additionally, the elemental portions are distributed over the support so as to be in contiguous relation to each other and to form a pattern on the support which simulates a color screen type of pattern.

A general feature of a multicolor photosensitive element resides in the placement or location of the selectively sensitive elemental portions in side-by-side relation so that each elemental portion of the photosensitive element is individually exposable only by light directed sole- This is advantageous the differently sensitive elemental portions since filter media which are associated with each such a portion will modify only the exposure light incident thereon.

A number of procedure for the production of photosensitive elements vand film assemblies employable for carrying out multicolor reproduction have beeen disclosed in the previously-mentioned applications Serial No. 176,-

961 (now abandoned and replaced by application Serial No. 448,441, filed August 9, 1954, now US. Patent No.

2,968,554) and Serial No. 358,011 (now abandoned and replaced by application Serial No. 577,711, filed April 12, 1956). One multicolor negative .or photosensitive element formed in accordance with practices described in my application Serial No. 358,011 is shown in Fig. 3 as comprising a support 40 having thereon three sets of selectively sensitive blue, green and red elemental portions 500, 600 and 700 wherein the individual portions 500 are illustrated in spaced relation to each other and with the selectively sensitive portions 600 and 700 interspersed therebetween in inlaid relation.

positelayer formed of a plurality of strata which are piled or superposed one on the other and each of which contains photosensitive silver halide or a material which assists or contributes to image formation or the control thereof. By this last-mentioned procedure, a stratum containing the dye developer may be located between the support and the photosensitive material.

By one practice set forth inmy application Serial No. 358,011, a support 40 such as that shown in Fig. 3 is coated with a layer 50 comprising a mixture of all the materials needed to provide the blue-sensitive portions 500 and is embossed to provide spaced-apart depressed sections or grooves into each of which there is doctored a mixture of all of the materials needed to provide the green-sensitive elements 600. Another embossing step is carried out to provide another set of spaced-apart 1 depressed sections or grooves into each of which there is doctored a mixture of all of the materials needed to provide the red-sensitive elements 700.

If layer 50 is is one stratum thick, it comprises a mixture of a blue-sensitive silver halide emulsion in which a yellow dye developer has been incorporated.

If the layer 50 is a composite layer, i.e., contains two or more strata, it comprises a stratum 52 containing a yellow dye developer and a stratum 54 of blue-sensitive silver halide emulsion superposed thereon as illustrated in Fig. 4. I

If a layer 60 which provides the green-sensitive elements 600 is one stratum thick, it comprises a mixture of a green-sensitive silver halide emulsion in which a magenta dye developer has been incorporated and preferably includes a yellow filter material such as a pigment or dye which is insoluble in the liquid processing composition. Similarly, if a layer 70 which provides the redsensitive element 7 00 is one stratum thick, it comprises a mixture of a red-sensitive silver halide emulsion, a cyan dye developer and a yellow filter material.

If a layer 60 or 70 is a composite layer such as shown in Figs. 5 and 6, it comprises a stratum of insulating material, a stratum of dye developer, a photosensitive stratum and a filter material stratum. In Fig. 5, the insulating stratum, magenta dye developer stratum, green-sensitive silver halide stratum and filter material stratum are indicated respectively by the reference numerals 63, 62, 64 and 65, while in Fig. 6 the insulating stratum, cyan dye developer stratum, red-sensitive silver halide stratum and the filter material stratum are indicated respectively by the reference numerals 73, 72, 74 and 75.

In the multicolor photosensitive element such as that of Fig. 3, the green-sensitive elemental portions are seated in the depressed sections of a relief impression formed in the element by the first embossing step and are supported upon layer 50. Also, the red-sensitive elemental portions are similarly supported upon layers of other sensitivities. There is an undesirable tendency for liquid which is used to process a photosensitive element and which has penetrated or permeated through an overlying light-sensitive elemental portion and into an underlying layer, to transport image-forming materials from the underlying layer.

In instances where the light-sensitive elemental portions are one stratum thick, penetration control may be eifected by a number of practices such, for example, by the thickness of each silver halide emulsion layer as well as by other practices as set forth in my application Serial No. 358, 011 (now abandoned and replaced by application Serial No. 577,711, filed April 12, 1956).

In instances where the light-sensitive elemental portions comprise composite layers, a stratum of an insulating material provides convenient penetration control.

1 Such strata are located between superposed emulsions but not over portions of an emulsion which remain uncovered by any other emulsion. Examples of such materials are cellulose nitrate, cellulose acetate, cellulose butyrate, partially hydrolyzed polyvinyl acetate, nylon-type plastics and the like.

Compositions for providing an insulating stratum such as the strata 63 and 73 and which may be doctored into a depressed section of a relief impression in a multicolor negative element comprise a suitable organic solvent in which the plastic is dissolved.

As is understood in multicolor photography, it is desirable to expose the green-sensitive and red-sensitive emulsions through a blue absorbing or yellow filter. For this purpose, a pigment or a dye, which is substantially insoluble in the processing composition and substantially unreactable or inert with respect to the developer and silver halide, is employed in the greenand red-sensitive elemental portions. One excellent material for this purpose, as pointed out in my application Serial No; 358,011 (now abandoned and replaced by application Serial No. 577,711, filed April 12, 1956), is a pigment comprising a suspension of a benzidine yellow.

If the greenor red-sensitive layers are one stratum thick, the yellow filter material may be incorporated in I7 the silver halide emulsion by any practice similar to those employed for distributing a developer therein.

If the filter material is employed in a composite layer, it is embodied into a suitable composition for doctoring into a depressed section of the embossed relief impression. A composition for this purpose comprises a mixture of a pigment, gelatin and water.

A photosensitive element like that of Fig. 3 is available for use in conjunction with a print-receiving element 15 in a film assembly of the character illustrated in Fig. 7.

Exposure of the photosensitive element 100 of the film assembly of Fig. 7 is preferably carried out in similar manner to that described, namely, from the emulsion side thereof. The mechanisms previously discussed in regard to the transfer of unreacted dye developer to the exclusion of its immobilized oxidation product occurs for each individual selectively sensitive portion of the multicolor negative.

In carrying out the processing, the positive print-receiving element is arranged similar to the manner set forth in the previously-mentioned applications Serial Nos. 176,961 (now abandoned and replaced by application Serial No. 448,441, filed August 9, 1954, now US. Patent No. 2,968,554) and Serial No. 358,011 (now abandoned and replaced by application Serial No. 577,711, filed April 12, 1956), so that the dye developers in each imagewise distribution will provide subtractive dyes on the print receiving element which together form the desired positive multicolor print. It is preferable to space the positive print-receiving element from the negtive color screen type photosensitive element so that the dye developers of each imagewise distribution will be diffused sidewise or laterally from the negative element whereby dye developers transported from adjacent selectively sensitive elemental portions will overlap and provide mixtures of subtractive dyes on the print-receiving element. Thus, it will be appreciated that unoxidized reagent which is transferred in the described manner is deposited on the print-receiving layer 15 of the film assembly of Fig. 7 to dye said layer and provide therein a reverse image in color of each latent image record in each set of the selectively sensitive portions from which unoxidized reagent is transferred.

Practices utilizing dye developers of this invention are subject to suitable variation to achieve certain of the modified results disclosed in my previously-mentioned copending application Serial No. 577,711. Thus, by the use of a dye developer which is black or of a mixture of dye developers which together provide black, the present invention may be practiced to produce both black and white negative and positive images. Similarly, the invention may be practiced so as to provide by transfer on a print-receiving element an image which is a composite record of a colored subject in terms of one or more colors and of silver or in terms of one or more colors and of a black dye. Likewise, the present invention is susceptible to practice to form either monochromatic or color negatives with the use of the types of photosensitive elements disclosed herein.

A consideration of the foregoing disclosure will bring out the desirable advantages attained by the utilization of the processes and practices forming the subject of this invention. The importance of these advantages becomes particularly manifest in comparison with prior practices such as those heretofore discussed for providing color images.

As evidenced by the disclosure, all practices herein are carried out with the use of a complete dye. Thus, there is no dye synthesis required during processing with its attendant disadvantages of possible low yields of dye and the formation of undesired by-products. Additionally, the processing set forth herein for the formation of color images is carried out with aminimum of reactions, pref- '1'8 erably, with a single reaction taking place in the negative? or photosensitive element and preferably with no reaction in the positive or print-receiving element. An important effect of theelimination of a reaction in the print-receiving element resides in the fact that it becomes unnecessary to incorporate an oxidant or other reactive material therein.

In prior practices where a different combination of reagents is employed to provide each dilferent color, the field from which appropriate materials may be selected is not only restricted by the number of materials available but also by the need for employing combinations of reagents which give reasonably similar processing performanceand which provide dyes of desired color characteristics. For example, in the field of color-forming development, only a limited number of color developers and coupler combinations which give reasonably similar processing performance are available for producing dyes which are of satisfactory colors and which are provided in the necessary quantities without the formation of undesired by-products. On the contrary, the procedures employed herein which make use of dye developers provide a profusion of reagents for the purposes of selection. Thus, there is a vastly increased possibility of selecting a set of two or more color-providing constituents which possess the optimum color characteristics and in addition give similar processing performance, such for example as by the selection of three differently colored dyes which all embody the same developing function and which all possess generally similar reaction rates.

An important feature of the invention resides in the provision of a developer which is itself of a desired color so that it is effectively a self-controlled dye which, at 10- cations where it is oxidized, becomes immobilized in the photosensitive element and substantially nontransferable therefrom. There is some tendency for the developer and/or other reagents to discolor the transfer print in instances where a separate developer, i.e., a. conventional developer which lacks a dye function, is utilized in conjunction with one or more other reagents to provide a desired color. The use in this invention of a developer which is a self-controlled dye avoids this undesirable discoloration.

Unlike many color processes which employ developers that are normally toxic in nature as a class, the dye developers of this invention may be selected to employ developing functions of a nature which are known to be nontoxic.

It is well accepted in the photographic art that acidsensitive dyes are undesirable for the purpose of providing color images due to their attack by reagents of an acidic nature which are frequently carried in the air. Due to the general ease with which a developing function may be combined with or added to a dye and due to the wide range for selection of dyes, the invention is preferably carried out with dyes which are acid resistant or which display acid resistance.

The invention employs developing functions, of which hydroquinone is an excellent example, which are recognized by the art as possessing more stability when neutral than certain other developers, for example, p-phenylenediamine developers. This desirable stability of the dye developers as utilized herein provides greatly increased storage stability for film units in which the dye developers are incorporated.

One other particular advantage derived from the practices herein set forth resides in the use of a minimum number of reagents and materials employed in the manufacture of the film units discussed herein. This fact leads to a considerable increase in the simplicity of manufacture as well as to simplicity in processing heretofore mentioned.

I have already described two film structures which are useful in the formation of multicolor images usinga plurality of selectively sensitized silver halide emulsions and a plurality of dye developers. One such embodiment utilizes a photosensitive element comprising a plurality of minute, difierentially sensitized photosensitive portions juxtaposed in a color screen pattern. I may also use a photosensitive element of the type prepared according to the procedures described in the copending United States patent application of Edwin H. Land at al., Serial No. 583,309, filed May 7, 1956, wherein a plurality of differentially sensitized silver halide emulsions in the form of lines or stripes are applied in side-by-side relationship on a support.

-'Another embodiment for obtaining multicolor transfer images utilizing dye developers employs an integral multilayer photosensitive element such as disclosed and claimed in the copending application of Edwin H. Land and Howard G. Rogers, Serial No. 565,135, filed February 13, 1956, wherein at least two selectively sensitized photosensitive strata are superposed on a single support and are processed, simultaneously and without separation, with a single, common image-receiving layer. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide emulsion stratum and a blue-sensitive sliver halide emulsion stratum, said emulsions having associated therewith, respectively, a cyan dye developer, a magenta dye developer and a yellow dye developer. The

dye developer may be utilized in the silver halide emul sion layer, e.g., in the form of particles, or it may be employed as a layer behind the appropriate silver halide emulsion strata. Each set of silver halide emulsion and associated dye developer strata may be separated from the other sets by suitable spacer strata, for example, by alayer of gelatin or polyvinyl alcohol. One may also use barrier layers, e.g., a layer of a slowly permeable material, such as a layer of cellulose acetate hydrogen phthalate containing cellulose acetate, alone or in combination with a spacer layer.

-A multilayer photosensitive element of the type just mentioned is illustrated in Fig. 9 of the accompanying drawings. A support 40 carries a layer 72 containing a cyan dye developer; a layer 74 of a red-sensitive silver halide emulsion; a spacer layer 80, e.g., of gelatin or polyvinyl alcohol; a layer 62 containing a magenta dye developer; a layer 64 of a green-sensitive silver halide emulsion; a spacer layer 80; a layer 52 containing a yellow dye developer; and an outermost layer 54 of a blue-sensitive silver halide emulsion. In certain instances, it may be desirable to incorporate a yellow filter in front of the green-sensitive emulsion layer, and such yellow filter may be incorporated in the spacer layer. Where the yellow dye developer is of the appropriate color and present in a state capable of functioning as a yellow filter, a separate yellow filter may be omitted.

. .Referring again to Fig. 9, the multilayer photosensitive element is shown in spread-apart relationship (as, for example, during exposure) with an image-receiving element having mounted thereon a rupturable container 17 holding a processing composition. The image-receiving element comprises a support 11 and an image-receiving layer 15. After exposure, the image-receiving element is brought into superposed relationship with the multilayer photosensitive element and the rupturable container 17 ruptured by application of suitable pressure, e.g., by advancing between a pair of rollers, not shown, and a layer of the liquid composition spread between the superposed elements. After a suitable imbibition period during which at least a portion of the dye developer associated with unexposed areas of each of said emulsions is transferred to the superposed image-receiving element, the latter element is separated to reveal the image.

vThe following example illustrates the preparation such amultilayer photosensitive element.

'20 'Example 1.-

An integral multilayer photosensitive element similar to that shown in Fig. 9 of the accompanying drawing may" be prepared in a manner similar to that described in Example 2 of the aforementioned copending application. Serial No. 565,135. This photosensitive element com-.

prises the following layers, laid down in the order recited, on a suitable support, e.g., a gelatin-coated film base:

(1) A polymeric layer containing a cyan dye developer,

i.e., 1,4-bis-[/3-(2',5'-dihydroxyphenyl)-propylamino]- anthraquinone. (2) A red-sensitive silver halide emulsion layer (3) A layer of polyvinyl alcohol as a spacer layer.

(4) A polymeric layer containing a magenta dye.de-.

. veloper, i.e., 2-[p-(2'-,5'-dihydroxyphenethyl)-phenylazo] -4-n-propoxy-1-naphthol.

(5) A green-sensitive silver halide emulsion layer.

(6) A layer of polyvinyl alcohol as a spacer layer.

(7) A polymeric layer containing a yellow dye developer,

i.e., 1-phenyl-3-N-n-hexyl-carboxamido-4-[p-(2",5"-dihydroxyphenethyl) -phenylazo] -5-pyrazolone.

(8) A blue-sensitive silver halide emulsion layer.

An example of suitable processing composition for use with such a multilayer photosensitive element comprises an aqueous solution comprising:

I Percent Sodium carboxymethyl cellulose 4.5 Sodium hydroxide 3.0 1-phenyl-3-pyrazolidone 0.6 2,S-bis-ethyleneimino-hydroquinone 0.4 6-nitrobenzamidazole 0.12

As I have stated before, dye developers are silver halide' developing agents which are dyes. They are capable of developing exposed silver halide and do, in fact, develop exposed silver halide.

I have further discovered, however, that processes" amples of suitable developing agents, mention may be made of Metol (mono-N-methyl-p-aminophenol), Amidol (2,4-diaminophenol), N-benzylaminophenol, toluhydrw quinone and Phenidone (1-phenyl-3-pyrazolidone).

The use of an auxiliary developing agent is particularly advantageous in that it gives cleaner highlights and better intermediate tones. In some instances, however, use of auxiliary developing agents which form colored oxidation products may give rise to some staining of the highlights or light steps of the transfer images. In some cases,

the use of Metol may result in some grey stain. I have found, however, that the use of a 3-pyrazolidone developing agent not only eliminates the grey stain observed with the use of developing agents, such as Metol, but also gives transfer images of improved contrast and speed.

' The 3-pyrazolidone developing agents may be repre-- sented by the general formula:

in which R R R3, R and R each represents substituents such as hydrogen, aryl or alkyl groups, including substituted alkyl and aryl groups. The alkyl groups preferably contain from 1 to 4 carbon atoms, inclusive, e.g., methyl, ethyl, isopropyl, butyl, etc., and the alkyl groups may be substituted, e.g., by hydroxyl groups. The aryl groups also may be substituted, e.g., by hydroxyl, amino, alkoxy, oxyalkyl, substituted amino, nitro, halogen, sulfonic or carboxylic groups. The aryl groups are preferably of the benzene or naphthalene series. A large number of developing agents within this class of 3- pyrazolidones are reported in the literature; see, for example, U.S. Patent No. 2,289,367, issued July 14, 1942, to John C. Kendall; US. Patent No. 2,691,589, issued October 12, 1954, to Richard W. Henn et al.; and US. Patent No. 2,731,300, issued June 19, 1956, to Thomas H. James et al. A particularly useful developing agent of this class is 1-phenyl-3-pyrazolidone, which is commercially available under the trademark Phenidone from Ilford, Ltd.

The auxiliary developing agent may be contained in the processing composition, or in one or more layers of the photosensitive element, e.g., in the silver halide emulsion layer or in the layer containing the dye developer. In some instances, it may be desirable to have a portion of the auxiliary developing agent in the processing composition and the remainder distributed in one or more layers of the photosensitive or negative element. Where the auxiliary developing agent is contained in the processing composition, it has been found that from about 0.05% to about 1.0%, by weight, of the auxiliary developing agent is effective to produce the improved results.

The following examples illustrate the use and advantages of a 3-pyrazolidone auxiliary developing agent:

Example 2 A photosensitive element was prepared containing a layer of 2-naphthylazo-hydroquinone dye developer behind the silver halide emulsion. This photosensitive element was exposed and an aqueous liquid processing composition comprising Percent Metol 0.2 Sodium hydroxide 2.0 Potassium bromide 0.2 Sodium oarboxyrnethyl cellulose 4.5

Example 3 The procedure described in Example 1 was repeated using 0.2% of 1-phenyl-3-pyrazolidone in the liquid processing composition instead of Metol. The resulting yellow positive image showed no grey color in the light steps.

Example 4 The procedures described inrExarnples 1 and '2 were repeated, using 1,4-bis-[fi-(2',5'-dihydroxyphenyl)-ethylamino]-anthraquinone dye developer in lieu of the 2- naphthylazohydroquinone dye developer. The cyan positive obtained using 0.2% of 1-phenyl-3-pyrazolidon' showed increased density and improved. contrast and speed as compared to the cyan positive image obtained using 0.2% Metol in the liquid processing composition.

it will be understood that one may use more than one auxiliary developing agent. The advantages of using a combination of a B-pyrazolidone developing agent and a benzenoid developing agent, particularly in connection with multilayer photosensitive elements, such as that described in connection with Fig. 9, are described and claimed in the copending application of Howard G. Rogers and Harriet W. Lutes, Serial No. 654,781, filed April 24, 1957. At set forth in that application, benzenoid developing agents contain an aryl nucleus, e.g., a benzene or naphthalene nucleus, substituted in the ortho or para positions, with respect to each other, by hydroxyl and/ or amino groups, including substituted amino groups, and this nucleus also may have other nuclear substituents, e.g., alkyl, aryl, arylthio, etc. The benzenoid developing agents form quininoid oxidation products. As examples of suitable developing agents within this group, mention may be made of the following:

I have further found that dye developers may be immobilized without having them react directly with exposed silver halide. This indirect reaction and the resulting formation of a less soluble, substantially immobile oxidation product may be accomplished by developing at least a portion of the exposed silver halide with another or cooperative developing agent which is not a dye, and reacting an oxidation product of said developing agent with the dye developer. This reaction results in the formation of a less mobile oxidation product of the dye developer and the regeneration of the cooperative developing agent. This interaction or energy transfer reaction is most efiective with dye developers whose oxidation products have a substantially lower solubility in the processing composition than does the oxidation product of the cooperative developing agent.

By way of recapitulation, I have discovered (a) that one may use the reaction directly between a dye develop er and exposed silver halide to form a less mobile reaction product of the dye developer, and (b) that one may use the reaction between a dye developer and the oxidation product of a cooperative developing agent (formed by development of exposed silver halide by the cooperative developing agent) to form the desired less' mobile reaction product of the dye developer. It will be understood that both of the above mechanisms (at) and (b) may be employed in the development of a latent image and the formation of an imagewise distribution of mobile dye developer. Mechanism (b) may occur where. the additional developing agent is used in an accelerating quantity to reduce the induction period, but it is particularly significant if the additional developing agent is used in an amount in excess of an accelerating amount, for example, an amount which is equal to or greater than the amount of dye developer, on a molar basis. In this last instance, a substantial amount of the development is believed to be performed by the additional developing agent, the dye developer being immobilized by reaction with oxidized cooperative developing agent.

The interaction of oxidized developing agent and a dye developer has been demonstrated in several ways. In one set of experiments, 1.2 g. of a magenta dye developer, 2- [p- 2,5 '-dihydroxyphenethyl -phenylazo] -4- methoxy-l-naphthol, was ground to a paste in 4 cc. of water and this paste was mixed with 30 cc. of a greensensitive silver halide emulsion. After coating and exposure, development was effected, using an aqueous processing composition comprising:

Percent Sodium carboxymethyl cellulose 4.5 Sodium hydroxide 3.0 1-phenyl-3-pyrazolidone 0.6 N-benzyl-p-aminophenol 0.4 6-nitrobenzimidazole 0.16

After transfer was completed, the developed negative was examined. The unexposed areas of the negative were colored magenta, but the exposed areas were uncolored or only very slightly colored, indicating that the dye developer in the exposed areas did not dissolve to any appreciable extent. It is believed that the molecules of dye developer on the surface of the dye developer particles were oxidized by an energy transfer reaction between the dye developer and oxidized developing agent before the particles of dye developer could dissolve and react directly with exposed silver halide. When used without such an added developing agent, the same magenta dye developer will develop exposed silver halide by itself.

In another set of experiments, a cyan dye developer, 1,4 bis [,6 (2',5' dihydroxyphenyl) propylamino]- anthraquinone, was dispersed in a layer of gelatin, over which a red-sensitive silver halide emulsion was coated. After an overall exposure, the negatives were developed using (1) a processing composition containing only sodium hydroxide and sodium carboxymethyl cellulose and (2) a processing composition like (1) but to which had been added an antifoggant and l-phenyl-3-pyrazolidone and 2,5-bis-ethyleneimino-hydroquinone. The photosensitive element and the image-receiving elements were separated after two seconds and the negatives were washed. Photomicrographs of negatives developed with each of these solutions were made, including negatives from which the silver was fixed out.- Examination of the negative processed with the composition (1) which contained no additional developing agent showed that the cyan dye developer had diffused through the emulsion and had developed exposed silver halide throughout the emulsion. Examination of negatives processed with the composition (2) which contained additional developing agents showed that exposed silver halide was developed throughout the emulsion layer, but that the cyan dye developer had been immobilized in the lower portion of the emulsion layer, and that some of the cyan dye developer had been immobilized in the gelatin layer itself.

It should now be apparent that the use of a developing agent in addition to the dye developer and the immobilization of a dye developer by reaction with the oxidation product of such an additional developing agent offers a means of obtaining faster development of the latent image and better control of the dyedeveloper. It also permits the efficient use of dye developers which might be con- '24 sidered to be weak or slow developing agents, e.g., dye developers containing a 1 grouping, as well as dye developers which might have a diffusion rate faster than their development rate in the absence of the additional developing agent.

I have also found that it is frequently very useful to effect development with a dye developer in the presence of an antifoggant. The antifoggant is particularly helpful in minimizing or preventing reaction of a dye developer with unexposed silver halide. The antifoggant may be added to the processing composition, to one or more layers of the photosensitive element, or to both the proc-' essing composition and the photosensitive element. As examples of antifoggants which are useful, mention may be made of inorganic antifoggants, such as sodium and potassium bromide and iodide, and organic antifoggants, such as 6-nitro-benzimidazole, benzotriazole, chloro-j benzotriazole, 5 methyl benzimidazole, 2 amino-' benzimidazole, S-nitro-benzimidazole, and thioacetanilide. The use of organic antifoggants has been found to be particularly desirable in the processing of multilayer negatives, e.g., such as that shown in Pig. 9.

I have also discovered that increased positive image density may be obtained by adding a water-miscible, organic solvent to the processing composition. The wa-' ter-miscible solvent should be one which will increase the solubility in the processing composition of the unreacted dye developer .without substantially increasing the solubility of the reacted or oxidized dye developer, and the quantity used is such as to achieve this result. As examples of suitable organic, water-miscible solvents, mention may be made of methanol, ethanol, tetrahydro-' furan, acetone, dimethyl formamide, morpholine and phenyl ethanol.

After the image-receiving layer is separated from the photosensitive element, one or more additional transfer images may be obtained by processing the separated negative with a fresh image-receiving layer and a processing composition which contains a solvent for unreacted dye developer but should not dissolve any appreciable amounts of the reacted dye developer associated with the exposed areas of the emulsion.

The image-receiving element may contain agents adapted to mordant or otherwise fix the difiused, unoxidized dye developer. Thus, where the dye developer contains an o-dihydroxybenzene group, it may be fixed after transfer by forming a complex with an aluminum salt, as disclosed and claimed in my copending U.S. application, Serial No. 734,860, filed May 13, 1958.

Although in the above description of the various embodiments of this invention the image-receiving layer has been separated from the silver halide emulsion or emulsions after transfer has been effected, separation need not be effected if the image-receiving element is transparent and a processing composition containing a substance rendering the dried processing composition layer opaque is spread between the image-receiving layer and the silver halide emulsion or emulsions. in a preferred embodi ment, the processing composition contains a white pigment which provides an opaque background against which the positive image may be viewed. The use of opaque processing compositions to permit viewing of a transfer image without separation of the image-receiving layer and the photosensitive element is described in U.S. Patent No. 2,607,685, issued to Edwin H. Land on August 19, 1952. p

. Image-receiving layers which are particularly useful in processes of the type contemplated herein may be pre-' pared by dispersing (i.e., emulsifying) a relatively high boiling solvent for unreacted dye developer in a watermiscible plastic. The high boiling solvent should have very low solubility in water. Image-receiving elements of this type offer a number of advantages, including improved color and stability of the transfer image. Thus, for example, a dye image formed in an image-receiving layer comprising tricresyl phosphate dispersed in polyvinyl alcohol exhibits greater brilliance than the same dye developer transferred to polyvinyl alcohol.

Although this application is particularly concerned withthe formation of positive transfer images by retaining oxidized dye developer in the negative element, and the invention has been illustrated by the use of dye developers which have a less mobile reaction product, I may obtain negative transfer images by utilizing a dye developer which, upon oxidation as a function of development, provides a more mobile reaction product, so that the reacted dye developer is more mobile than the unreacted dye-developer.

It will be noted that the transfer image formed by the transfer of unreacted dye developer is a dye image. I have discovered, however, that I may also. transfer unreacted silver halide from unexposed areas of the silver halide emulsion to the image-receiving layer and there precipitate it as silver, To accomplish this, I add to the processing composition a silver halide solvent, i.e., a reagent capable of forming a soluble, diffusible silver halide complex. The amount of silver precipitated on the image-receiving layer may be controlled by the amount and/or kind of silver precipitating agent used, in accordance with practices well known in the silver diffusion transfer art. The transfer of silver is useful in dye developer processes involving the formation of blackand-white transfer images, and is also useful in obtaining increased image density in color images. As an example of a suitable silver halide solvent, mention may be made of sodium thiosulfate, although other well known silver halide solvents may be used.

I have previously referred to the use of a dye developer to control the transfer of another dye which is not a developing. agent. The following example illustrates this technique:

Example 5 A negative was prepared by coating a film base with a layer of gelatin containing a cyan dye, Colour Index No. 518. Over this layer of cyan dye was coated a layer of cellulose acetate hydrogen phthalate containing a yellow dye developer, Z-(B-naphthylazo)-hydroquinone.-

After exposure, the negative was processed in superposed relationship with an image-receiving element (comprising polyvinyl alcohol coated on a baryta paper support) using an aqueous processing composition comprising:

Percent Sodium polyacrylate 0.6 Sodium hydroxide 1.5 Metol 0.2

After transfer was completed, the image-receiving element was separated and contained a green positive dye image of good contrast and density.

As noted before, the dye developer may be contained in the silver halide emulsion layer or in a layer behind the emulsion. In many instances, it is desirable to use the dye in a layer behind the emulsion. Such layers containing dye developers may be coated from solvent systems, e.g., by the use of plastics which are soluble in coating compositions containing organic solvents in which the dye developers are soluble, or they may be coated from aqueous systems wherein a dye developer is dissolved in a substantially water-immiscible solvent, preferably a relatively high boiling solvent, and the resulting dye developer solution is then dispersed or emulsified into an aqueous solution of a water-soluble, hydrophilic plastic, e.g., gelatin. Techniques for forming such dis- 26 persions of water-immiscible solventsin aqueous solutions are well known in the art and may be used in preparing layers of dye developers for use in the processes of this invention.

The following example illustrates the formation of lay- Example 6 Z-(IB-naphthylazo)-hydroquinone (0.9 g.) was dissolved in 3.75 cc. of tricresyl phosphate and 3.75 cc. of ethyl acetate. This solution was then emulsified with 15 cc. of 2% aqueous gelatin and a wetting agent (Duponol ME) by passing the mixture through a colloid mill four times. The resulting dispersion was mixed with another 15 cc. of 2% aqueous gelatin and passed through the colloid mill three times, after which the dispersion was coated on a gelatin-coated cellulose acetate support. A blue-sensitive silver halide emulsion was then coated over the yellow dye layer. The resulting sheet was embossed to provide depresssed sections or grooves, in a direction 45 to the longitudinal axis of the sheet, A dispersion of a cyan dye developer in gelatin was prepared by dissolving 8%, by weight, of 1,4-bis-(2',5'-dihydroxyphenethylamino)-anthraquinone in 3 cc. of tricresyl phosphate and 3 cc. of ethyl acetate, mixing this solution with 15 cc. of a 20% aqueous gelatin solution and passing the mixture through a colloid mill five times. The resulting dispersion was doctored into the grooves, followed by a green-sensitive silver halide emulsion. A yellow filter (Padding Yellow GL: a benzidine yellow pigment) was then doctored into the grooves containing the cyan dye developer dispersion and the green-sensitive silver halide emulsion.

In some instances, it may be desirable to include in the processing composition a reagent which will soften gelatin, and thereby aid in transferring the mobile dye dc veloper to the image-receiving layers. Examples of such a gelatin-softening reagent include urea, sodium thiocyanate and the sodium salt of 2,5-dimethylbenzene sulfonic acid, but it will be understood that other agents of this type are known to the art and may be used for this purpose.

Dye developers may be dispersed in a silver halide emulsion by techniques known in the art and similar to those employed in Example 6.

I have already pointed out that a dye developer utilized in a photosensitive layer should exert negligible absorption upon light used to expose the photosensitive element. In addition to using the dye developer in the form of low covering power particles, one may employ the dye developer in a dichroic state, as disclosed and claimed in the copending application of Edwin H. Land, Serial No. 607,820, filed September 4, 1956. Some dyes exhibit a pH sensitivity such that they absorb at a lower wavelength in a neutral or acidic environment and exhibit a bathochromic absorption shift in an alkaline environment. This property may also be utilized to reduce or eliminate absorption of light required to expose emulsion. Another method is to utilize a dye developer which, in the emulsion layer, does not absorb exposure light but which undergoes a color change after transfer, as by forming a metal complex on the image-receiving layer. One such technique is that disclosed and claimed in my copending application Serial No. 734,860, filed May 13, 1958. As shown in that application, the formation of an aluminum complex of Z-naphthalene azo catechol was efiective to shift the color of the positive dye image from yellow to orange. Another method of obtaining a re as by hydrolysis, will effect a bathochromic color shift to provide the desired positive image dye color.

.27 A number of dye developers suitable for use in the transfer processes of this invention have been described above. Mention has also been made of a number of ways by which a silver halide developing group, e.g., a hydroquinonyl radical, may be attached to a dye. Additional dye developers useful in the processes of this invention, as well as processes for the Preparation of such dye developers, are disclosed and claimed in the following copending United States patent applications:

Serial No. Applicant (s) Filed July 22, 1954 (now abandoned in favor of Serial Nos. 849,748 and 849,726, filed October 30, 1959).

August 16, 1954 (now abandoned in favor of Serial No. 755,804, filed August 18, 1958). 1

August 12, 1954 (now abandoned in favor of Serial No. 849,727, filed October 30, 1959).

September 29. 1954 (now abandoned in favor of Serial Nos. 771,719 and 771,718, filed November 4, 1958).

November 26, 1954 (now abandoned in favor of Serial Nos. 1,448 and 1,442, filed January 11, 1960).

February 3, 1955.

November 3. 1954 (now abandoned in favor of Serial Nos. 748,146 and 748,145, filed July 14, 1958).

445,171..-- R. S. Corley 450,205-.-. E. R. Blout at 211......

449,514..-. --do 459,198...- ...-do

485,840...- do 466,682...- M. Green et al 473,458.... E. R. Blout et al December 6, 1954. 478,922. do December 30, 1954 (now abandoned in favor of Serial Nos. 824,785 and 824,786, filed July 3, 1959). 478,192.- do December 28, 1954 (now abandoned in favor of Serial No. 760,309, filed September 11, 1958). 485,342...- R. S. Corley- January 31, 1955. 521,874.." E. R. Blout et al July 13, 1955 (now abandoned in favor of Serial Nos. 799,426 and 799,427, filed March 16, 1959). 522,848-..- do July 18, 1955 (now abandoned in favor of Serial Nos. 799,485 and 799,425, filed March 16, 1959). 612,045- September 25, 1956.

Do. Do. Do. Do. August 27. 1957. June 6, 1957. July 5, 1957. 711,8l1 do January 29, 1958. 680,437.... August 26, 1957. 707,109 d January 6, 1958. 685,081.-. September 20, 1957. 680,403- August 26, 1957. 680,434 .(1 Do. 678,439..- M. S. Simon August 15, 1957. 1 697,808.... M. S. Simon et al November 21, 1957 (now abandoned in favor of Serial No. 813,701, filed May 18, 1959). 697,809.... E. R. Blout et al November 21, 1957 (now abandoned r in favor of Serial No. 813,702,

filed May 18, 1959). 709,005...- S. Kasman et al January 15, 1958. 703,515...- M. Green December 18, 1957. 709,002..-- M. Green et al January 15, 1958.

This application is a continuation-in-part of my copending US. patent applications, Serial No. 415,073, filed March 9, 1954, now abandoned, andSerial No'. 518,979, filed June 29, 1955, now abandoned.

The terms silver halide developing agent and silver halide developer have been used interchangeably herein in their art-accepted meaning as denoting a reagent, i.e., compound, which is capable of reducing silver halide to silver and which is capable, under the conditions of photographic processing, of preferentially reducing ex posed silver halide, i.e., of developing a latent image in an exposed silver halide emulsion.

Since certain changes may be made in the above process without departing from thescope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: t

V 1. A process of forming positive transfer images in color comprising the steps of: permeating an exposed photosensitive element, including a photosensitive silver halide emulsion, with a liquid composition and, during said permeation, having said photosensitive element so superposed on an image-receiving layer formed of a dyeable material that said liquid has access to said dyeable material; providing within the lamination comprising said photosensitive element and said image-receiving layer at least one dye developer which is soluble in said liquid and which when dissolved therein is mobile in said lamination,said mobile dye developer being a compound which is both a silver halide developing agent and a dye having a predominant visible spectral absorption within the regionof the spectrum to which said silver halide emulsion is sensitive, said dye developerbeing further characterized by providing an oxidation product which is of lower mobility in said liquid than the unoxidized dye developer, developing said exposed photosensitive material and forming said oxidation product by reaction of the developer portion of said dye developer in said exposed areas; transferring by difiusion to said image-receiving layer'at least a part of the unoxidized dye developer and depositing said unoxidized dye developer upon said imagereceiving layer to dye said layer whereby a visible image is created by said transferred dye developer, and including the step of separating said image-receiving layer and said photosensitive element from their superposed relationship at some stage of said process after said unoxidized dye developer has been transferred to said image-receiving layer. V

2. A process of forming positive transfer images in color as defined in claim 1, wherein said dye developer is so distributed within said lamination as to have a sub stantially uniform concentration per unit surface area of said lamination, and said concentration is in excess of that quantity thereof which is needed to cause said dye developer to be substantially completely reacted in fully exposed and developed unit areas. 7

3. A process of forming positive transfer images in color asdefined in claim 1, whereinsaid dye developer is contained within said photosensitive element and is char: acterized by the property of hardening the carrier matevrial of said silver halide where said silver halide is developed to silver and said dye developer is oxidized.

. 4. A process of forming positive transfer images in color as defined in claim 1, wherein said dye developer is contained in said photosensitive element in a stratum of material which is permeable to said liquid and which is located between a support and a stratum of a permeable material within which said photosensitive silver halide is distributed.

5. The process of forming transfer images in color as defined in claim 4, wherein said stratum containing said dye developer comprises cellulose acetate hydrogen phthalate. 6. The process of forming transfer images in color as defined in claim 4, wherein said stratum containing said dye developer comprises gelatin. i 7. A process of forming positive transfer images in color as defined in claim 1, wherein said dye developer is contained in said photosensitive element prior to exposure thereof, and said photosensitive element also includes a dye which is not a silver halide developing agent, said dye being restrained from transfer to said image-receiving layer by the action of said oxidation product of said dye developer. V 8. A process of forming positive transfer images in color as defined in claim 7, wherein said dye is a dye possessing a coupling function capable of coupling with the oxidation product of said dye developer.

'9. A process of forming positive transfer images color as defined in claim 7, wherein said dye developer has an oxidation product which is substantially unreactable with said dye and which is further characterizedby possessing the property of hardening the carrier material of said silver halide where said silver halide is developed to silver and said dye developer is oxidized.

10. A process of forming positive transferimages in color as defined in claim 1, wherein said silver halide'is contained in a polymericmaterial capable of coupling with the oxidation product of said dye developer.

11. A process as defined in claim 1, wherein said development is effected in the presence of a silver halide solvent capable of forming a soluble silver complex with unexposed silver halide.

12. A processas defined in claim 1, wherein said developrnent is effected in the presence of at least one silver halide developing agent which is substantially colorless in at least its unoxidized form.

13. A process of forming tra'n'sfer images in color comprising developing an exposed photosensitive element including a silver halide emulsion with a developing composition containing a dye developer, said dye developer being a compound which is both a silver halide developing agent and a dye, whereby saiddye developer is oxidized as a function of said development to provide an oxidation product which is substantially less mobile in said developing composition than is unoxidized dye developer, said unoxidized dye developer having a predominant spectral absorption within the region of the visible spectrum to which said silver halide emulsion is sensitive, transferring by diffusion at least a portion of said unoxidized dye developer from undeveloped areas of said silver halide emulsion to a superimposed image-receiving layer whereby a visible image consisting essentially of said unoxidized dye developer is created.

14. The process of forming transfer images in color comprising the steps of developing an exposed photosensitive element including a gelatino silver halide emulsion with a solution containing a dye developer, said dye developer being a compound which is both a dye and a silver halide developing agent capable of tanning gelatin, retaining in said photosensitive element containing said silver halide emulsion, substantially all of the dye developer oxidized by said development, transferring by imbibition at least a portion of the unoxidized dye developer from unexposed areas of said silver halide emulsion to an image-receiving layer so superposed on said silver halide emulsion as to receive the transferred, unoxidized dye developer without substantially disturbing its imagewise relation to the developed latent image, said unoxidized dye developer having a predominant spectral absorption within the region of the visible spectrum to which said silver halide emulsion is sensitive, and causing said transferred, unoxidized dye developer to dye said image-receiving layer and impart thereto a positive dye image of substantially the samecolor as said unoxidized dye developer.

15. The process of forming transfer images in color comprising'the steps of exposing a photosensitive element containing a silver halide layer, permeating said exposed silver halide layer with a. liquid composition to provide a solution of a dye developer, said dye developer being a compound which is both a silver halide developing agent and a dye, developing the exposed silver halide by means of said dye developer to provide an oxidation product of said dye developer which is substantially less mobile in said liquid composition than the unoxidized dye developer, transferring by diffusion at least a portion of the unoxidized dye developer from unexposed areas of said silver halide layer to an image-receiving layer so superposed on said silver halide layer as to receive the transferred dye developer without substantially disturbing its imagewise relation to the developed latent image, whereby without oxidation of said transferred dye developer, a visible positive dye image is created, said dye image having a predominant visible absorption within the region of the spectrum to which said silver halide is sensitive.

16. The process of forming transfer images comprising the steps of developing an exposed silver halide emulsion with a processing composition containing a dye developer, said'dye developer being acompound which contains a silvef halide developing function selected from the class consisting of orthoand para-dihydroxyphenyl groups,

and which compound is also a dye, said dye developer being further characterized in that, upon oxidation, a product less soluble and less mobile in said composition than is said dye developer is obtained, developing said exposed silver halide emulsion and forming said less soluble oxidation product as a function of said development, transferring by diffusion at least a portion of the unoxidized dye developer from undeveloped areas of said silver halide emulsion to an image-receiving layer so superposed on said silver halide emulsion as to receive the transferred, unoxidized dye developer, whereby a visible dye image is created by said transferred dye developer.

17. The process as defined in claim 16, wherein said dye developer is an azo dye.

18. The process of forming transfer images in color as defined in claim 16, wherein said dye developer is an anthraquinone dye.

19. The process of forming transfer images as defined in claim 16, wherein said processing composition contains a plurality of dye developers, said dye developers in admixture together providing black, and wherein said visible dye image is a black image.

20. The process of forming transfer images in color as defined in claim 16, wherein said image-receiving layer comprises polyvinyl alcohol.

21. The process of forming transfer images in color as defined in claim 16, wherein said image-receiving layer comprises gelatin.

22. The process of forming transfer images in color as defined in claim 16, wherein said image-receiving layer comprises N-methoxymethyl-polyhexamethylene adipamide.

23. The process of forming transfer images in color as defined in claim 16, wherein said image-receiving layer comprises particles of an organic solvent for said dye developer, said particles being dispersed on polyvinyl alcohol.

24. A process as defined in claim 16, wherein said development is effected in the presence of a hydroquinone silver halide developing agent which is substantially colorless in at least its unoxidized form.

25. The process as defined in claim 16, wherein said development is effected in the presence of a 3-pyrazolidone silver halide developing agent which is substantially colorless in at least its unoxidized form.

26. A process of forming positive transfer images in color as defined in claim 16, wherein said dye developer is initially present in said photosensitive element in a form whereby said dye developer exerts negligible absorption upon light which exposes said photosensitive element.

27. A process of forming positive transfer images in color as defined inclaim 16, wherein said dye developer is initially present in said photosensitive element in the form of particles having a low-covering power prior to exposure.

' 28. A process of forming positive transfer images in color as defined in claim 16, wherein said dye developer is present in said photosensitive element prior to exposure, and the color of said dye developer undergoes a bathochromic absorption shift upon solution of said dye developer in said processing composition.

29. The process of forming transfer images which comprises developing an exposed silver halide layer present in a photosensitive element and containing a latent image with a developing composition containing a black dye developer, said black dye developer being a compound which is both a silver halide developing agent and a black dye, oxidizing said black dye developer as a function of said development to form an oxidation product, said oxiclation product being less mobile in said composition than said dye developer, transferring by diffusion at least a portion of the unoxidized blackdye developer from unexposed areas of said silver halide layer to an imagereceiving layer so superposed on said silver halide layer as to receive said transferred, unoxidized black dye de- 31 veloper without substantially disturbing its imagewise relation to the developed latent image, whereby a positive black dye image is created by said transferred dye developer.

30. A photographic product comprising a support, at least one unexposed photosensitive silver halide emulsion contained in a layer carried by said support, each said silver halide emulsion having associated therewith a dye developer, said dye developer being a compound which is both a silver halide developing agent and a dye having a predominant absorption within the region of the visible spectrum to which'said silver halide emulsion is sensitive,

' said dye developer having an oxidation product which is less mobile than said dye developer.

31. A photographic product as defined in claim 30, wherein a layer carried by said support contains a silver halide developing agent which is substantially colorless in at least its unoxidized form.

v 32. A photographic product as defined in claim 30, wherein said photographic product includes a layer of gelatin positioned between each said silver halide emulsion and said support, associated said dye developer being dissolved in a water-immiscible solvent dispersed in said layer of gelatin.

33. A process of forming transfer images in color, comprising the steps of developing an exposed silver halide emulsion with a processing composition including a first silver halide developing agent and a second silver halide developing agent, said first silver halide developing agent being substantially colorles in at least its unoxidized form, said silver halide developing agent being a dye developer, said dye developer being a compound which is both a silver halide developing agent and a dyehaving a predominant absorption within the region of the visible spectrum to which said silver halide emulsion is sensitive, said dye developer having an oxidation product which is less mobile in said processing composition than is said dye developer, reducing at least a portion of the exposed silver halide within said first silver halide developing agent, reacting at least a portion of the oxidized first silver halide developing agent with said dye developer to form said less mobile oxidation product of said dye developer, forming an imagewise distribution of mobile dye developer as a result of the formation of said less mobile oxidation product of said dye developer as a function of the development of exposed areas, and transferring by diffusion at least a portion of said mobile dye developer from unexposed areas of said emulsion to a superposed image-receiving layer whereby a visible dye image of substantially the same color as said mobile dye developer is created.

34. A process of forming transfer images in color, comprising the steps of applying a processing composition and developing an exposed silver halide emulsion in the presence of a dye developer, said dye developer being a compound which is both a silver halide developing agent and a dye having a predominant absorption within the region of the visible spectrum to which said silver halide emulsion is sensitive, forming an oxidation product of said dye developer as a function of the development of said exposed silver halide emulsion, said oxidation product being less mobile in said processing composition than unreacted dye developer, and transferring by diffusion at least a portion of the more mobile, unreacted dye developer to a superposed image-receiving layer whereby a visible image is created by said more mobile, unreacted dye developer, said silver halide emulsion comprising a gelatin medium and said development being effected in the presence of a gelatin softening agent.

35. A process of forming transfer images in color, comprising the steps of applying a processing composition and developing an exposed silver halide emulsion in the presence of a dye developer, said dye developer being a compound which is both a silver halide developing agent and a dye having a predominant absorption within the region of the visible spectrumto which said silver halide emulsion is sensitive, forming an oxidation product of said dye developer as a function of the development of said exposed silver halide emulsion, said oxidation product being less mobile in said processing composition than unreacted dye developer, and transferring by diffusion at least a portion of the more mobile, unreacted dye developer to a superposed image-receiving layer whereby a visible dye transfer image is created by said more mobile dye developer, said development being effected in the presence of an organic solvent which increasesthe mobility of said unreacted dye developer.

36. A process of forming transfer images in color, comprising the steps of applying a first processing composition and developing an exposed silver halide emulsion in the presence of a dye developer, said dye developerbeing a compound which is both a silver halide developing agent and a dye'having a predominant absorption within the region of the visible spectrum to which said silver halide emulsion is sensitive, forming an oxidation product of said dye developer as a function of the development of said exposed silver halide emulsion, said oxidation product being less mobile in said processing composition than unreacted dye developer, and transferring by diffusion at least a portion of the more mobile, unreacted dye developer to a superposed imagereceiving layer whereby a first visible d'ye transfer image is created by said more mobile dye developer, seperating said image-receiving layer from said silver halide emulsion, applying to said separated silver halide emulsion a second processing composition which contains a solvent for said unreactedjmore mobile dye developer, superposing a second image-receiving layer on said separated silver halide emulsionfand transferring by diffusion unreacted dye developer from undeveloped areas, of said separated silver halide emulsion to said second imagereeeiving layer whereby a second visible dye image is created by said more mobile dye developer.

37. A process of forming transfer images in color, comprising the steps of applying a processing composition and developing an exposed silver halide emulsion in the presence of a dye developer, said dye developer being a compound which is both a silver halide develop ing agent and a dye having a predominant absorption within the region of the visible spectrum to which said silver halide emulsion is sensitive, forming an oxidation product of said dye developer as a function of the development of said exposed silver halide emulsion, said oxidation product being less mobile in said processing composition than unreacted dye developer, and transferring by diffusion at least a portion of the more mobile, unreacted dye developer to a superposed image-receiving layer whereby a visible dye transfer image is created by said more mobile, transferred dye developer,'said imagereceiving layer being transparent, said processing composition being located between said image-receiving layer and said silver halide emulsion, and said processing composition containing a reagent rendering opaque the layer of said processing composition, whereby said dye transfer image may be viewed without separating said imagereceiving layer and said silver halide emulsion.

38. A process as defined in claim 1, wherein said liquid composition includes a film-forming, viscosity-impart ing agent and is applied by being spread between said exposed photosensitive element and said image-receiving: layer as said exposed photosensitive element and said image-receiving layer are brought into superposed rela-- tionship.

39. A process as defined in claim 38, wherein said film-: forming, viscosity-imparting agent is sodium ,carboxymethyl cellulose. 7

4-0. Theprocess as defined in claim 16, wherein said dye developer is present prior to exposure in a photosensitive element containing a support carrying said silver halide emulsion, said dye developer being dissolved in a water-immiscible solvent dispersed in a layer of gelatin positioned between said silver halide emulsion and said support.

41. The process as defined in claim 16, wherein said image-receiving layer is positioned between said silver halide emulsion and a support carrying said silver halide emulsion, and including the step of separating said silver halide emulsion and said image-receiving layer after said transfer of unoxidized dye developer to said image-receiving layer.

42. The process as defined in claim 16, wherein said dye developer is initially contained in a layer carried by the support carrying said silver halide emulsion, and wherein said development is effected in the presence of a silver halide developing agent which is substantially colorless in at least its unoxidized form, which silver halide developing agent is initially contained in a layer carried by the support carrying said silver halide emulsion.

43. A process as defined in claim 14, wherein said dye developer contains a trihydroxyphenyl silver halide developing function.

44. A process as defined in claim 37, wherein said reagent rendering opaque said layer of processing composition is a white pigment.

45. A process as defined in claim 16, wherein said development is efifected in the presence of an organicantifoggant selected from the group consisting of 6-nitrobenzimidazole, Z-amino-benzimidazole, benzotriazole, chlorobenzotriazole, methyl-benzimidazole, 5 nitrobenzimidazole and thioacetanilide.

References Cited in the file of this patent UNITED STATES PATENTS 34 2,289,367 Kendall July 14, 1942 2,306,410 Schinzel Dec. 29, 1942 2,543,181 Land Feb. 27, 1951 2,543,691 Friedman Feb. 27, 1951 2,559,643 Land July 10, 1951 2,614,926 Land Oct. 21, 1952 2,647,049 Land July 28, 1953 2,661,293 Land Dec. 1, 1953 2,698,244 Land Dec. 28, 1954 2,698,798 Land Jan. 4, 1955 2,728,290 Marriage et a1 Dec. 27, 1955 2,751,300 James et a1. June 19, 1956 ,756,142 Yutzy July 24, 1956 2,892,710 Cohler et al. June 30, 1959 2,909,430 Rogers Oct. 20, 1959 FOREIGN PATENTS 498,875 Great Britain Jan. 10, 1939 503,752 Great Britain Apr. 11, 1939 634,169 Great Britain Mar. 15, 1950 900,266 France Sept. 25, 1954 53,515 France July 16, 1954 (Addition to No. 873,507) OTHER REFERENCES The Theory of Photographic Process, Mees, 1954, pp. 602-604.

Friedman: History of Color Photography, p. 369, 2nd to 4th lines after 2nd formulation, American Photo. Pub. Co., Boston, 1944.

Henn et al.: Photo. Science and Technique 1 (No. 4), 126-30 (1954).

Kendall: Brit. Jour. of Photo., January 30, 1953, vol. 100, pp. 56, 57.

Gilman: Organic Chem, vol. III, pp. 256 and 358 J. Wiley & Sons Inc., N.Y., 1953. 

1. A PROCESS OF FORMING POSITIVE TRANSFER IMAGES IN COLOR COMPRISING THE STEPS OF: PERMEATING AN EXPOSED PHOTOSENSITIVE ELEMENT, INCLUDING A PHOTOSENSITIVE SILVER HALIDE EMULSION, WITH A LIQUID COMPOSITION AND, DURING SAID PERMEATION, HAVING SAID PHOTOSENSITIVE ELEMENT SO SUPERPOSED ON AN IMAGE-RECEIVING LAYER FORMED OF A DYEABLE MATERIAL THAT SAID LIQUID HAS ACCES TO SAID DYEABLE MATERIAL, PROVIDING WITHIN THE LAMINATION COMPRISING SAID PHOTOSENSITIVE ELEMENT AND SAID IMAGE-RECEIVING LAYER AT LEAST ONE DYE DEVELOPER WHICH IS SOLUBLE IN SAID LIQUID AND WHICH WHEN DISSOLVED THEREIN IS MOBILE IN SAID LAMINATION, SAID MOBILE DYE DEVELOPER BEING A COMPOUND WHICH IS BOTH A SILVER HALIDE DEVELOPING AGENT AND A DYE HAVING A PREDOMINANT VISIBLE SPECTRAL ABSORPTION WITHIN THE REGION OF THE SPECTRUM TO WHICH SAID SILVER HALIDE EMULSION IS SENSITIVE, SAID DYE DEVELOPER BEING FURTHER CHARACTERIZED BY PROVIDING AN OXIDATION PRODUCT WHICH IS OF LOWER MOBILITY IN SAID LIQUID THAN THE UNOXIDIZED DYE DEVELOPER, DEVELOPING SAID EXPOSED PHOTOSENSITIVE MATERIAL AND FORMING SAID OXIDATION PRODUCT BY REACTION OF THE DEVELOPER PORTION OF SAID DYE DEVELOPER IN SAID EXPOSED AREAS, TRANSFERRING BY DIFFUSION TO SAID IMAGE-RECEIVING LAYER AT LEAST A PART OF THE UNOXIDIZED DYE DEVELOPER AND DEPOSITING SAID UNOXIDIZED DYE DEVELOPER UPON SAID IMAGERECEIVING LAYER TO DYE SAID LAYER WHEREBY A VISIBLE IMAGE IS CREATED BY SAID TRANSFERRED DYE DEVELOPER, AND INCLUDING THE STEP OF SEPARATING SAID IMAGE-RECEIVING LAYER AND SAID PHOTOSENSITIVE ELEMENT FROM THEIR SUPERPOSED RELATIONSHIP AT SOME STAGE OF SAID PROCES AFTER SAID UNOXIDIZED DYE DEVELOPER HAS BEEN TRANSFERRED TO SAID IMAGE-RECEIVING LAYER. 